AT509475B1 - METHOD FOR DRYING BULK GOODS - Google Patents

Description

Austrian Patent Office AT509 475B1 2012-01-15

Description: The invention relates to a method for drying bulk material, in particular solids, such as granules, powders, grains, films, chips, o. The like., Preferably plastic granules, in a drying silo by means of an air flow, wherein the exiting from the drying silo exhaust air Air flow or the return air in a drying or adsorbent-containing drying cell, preferably a wheel dryer, dried and fed back to the bulk material as a dry air stream and in the wheel dryer further the adsorbent is regenerated and cooled, wherein a rotatable drum of the wheel dryer is divided into at least three circle segments, wherein the area of a circle segment for drying or dehumidifying the exhaust air flow, the area of the second circle segment for heating the adsorbent and the area of the third circle segment for cooling the adsorbent is used.

For drying the emerging from the drying silo return air various methods and devices are known.

One of these known methods is shown in DE 36 25 013 A1. In the course of this known process, the exhaust air leaving the drying hopper is dried in a dryer containing an adsorbent and returned to the bulk material as dry air.

Furthermore, from DE 197 57 537 A1 discloses a method and apparatus for drying and heating of air, which is used for drying bulk material, known. This device essentially consists of at least one drying cartridge or drying cell, a downstream air heater, a downstream drying chamber or drying silo and a downstream cooling device.

Furthermore, from DE 101 18 762 A1 a method for the regeneration of moisture-laden process air is known. The atmospheric air is heated and fed to the drying cartridge to be regenerated. The subsequent re-cooling of the drying cartridge is carried out with a diverted from the dried process air partial air flow.

From EP 0 712 656 B1 a method for drying moist air is known and from EP 740 956 A2 a method and a device for processing a, in particular moisture, containing adsorbent.

Moreover, DE 2 025 205 A1 discloses a device with several chambers for the selective adsorption of molecules.

A device of the type indicated above is known from AT 505 391 B1. According to this device, the exhaust air stream is supplied to a, provided in the wheel dryer and connected to the adsorbent supply channel, deflected in the wheel dryer, passed over the adsorbent and then redirected as dry air flow and discharged in a discharge channel against the flow direction in the feed and fed to the drying silo , A disadvantage of this Radtrockners is that high pressures are necessary due to the high flow resistance due to the deflections.

All of the above-mentioned methods and devices have above all the disadvantages that the facilities require a very complex construction and in the process a high energy consumption for regeneration and drying is given.

The object of the invention is to provide a method of the type mentioned above, on the one hand avoids the above disadvantages and on the other hand, both in the purchase, as well as in operation, seen globally, the economy, especially in operation, increases.

The object is solved by the invention.

The inventive method is characterized in that the drying or. Dehumidification for the exhaust air flow and preferably the cooling of the adsorptive run parallel on parallel, in particular continuously in continuous operation, and the regeneration phase is carried out with the heating of the absorbent in the interval operation, the Drum of the Radtrockners is stopped in the cooling or regeneration phase and after completion of the cooling or regeneration phase to a selectable range, preferably the cooling range, further clocked and that the range for heating at least equal to or greater, preferably twice, than the area of cooling is determined. With the invention, it is possible for the first time to minimize energy consumption.

Zeolite needs to regenerate, ie for dehumidifying and drying a temperature above 200 ° C. The higher the temperature, the better the efficiency would be. For the regeneration of a certain amount of zeolite, therefore, a certain amount of energy, depending on temperature, time and air flow, necessary. Due to the degree of moisture of the zeolite, the optimum energy consumption can therefore be determined. Energizing beyond the saturation range is useless. With regard to the temperature resistance of the machine parts and components incorporated in the process, such as seals, which is around 280 ° C, however, the height of the temperature is limited.

As is known, the energy consumption of the drying process is very much determined by the heating power in the regeneration phase. According to the state of the art methods and their philosophy was to achieve a uniform dew point. Complying with this requirement, the regeneration phase was run in continuous operation.

According to the philosophy underlying the invention, namely to keep the quality standard of the dry air to existing plants at least, however, to increase the efficiency, it is deliberately differentiated in the drying process between strong and less heavily loaded drying tasks.

According to this conclusion, the regeneration phase is driven at less heavily loaded drying tasks in the interval operation according to the present inventive method. That is, the heater for heating the absorbent and optionally the associated fan are deliberately switched off for a period of time. With such an interval operation, the curve for the dew point runs only insignificantly different from the ideal curve, but the deviation for the quality standard is not noticeable.

Especially in tropical areas, methods with cartridges for drying due to the risk of leakage air are not in demand. In these areas thus wheel dryer of the type mentioned are used. In order to be able to operate such wheel dryer even more economically in operation, the present method is applied. In general, wheel dryers have the advantage of being self-sufficient and leak-free.

According to a particular feature of the invention, the range of drying or dehumidifying is about 240 degrees, the range for heating about 80 degrees and the area of cooling about 40 degrees. By this definition of the areas, that is to say to double the regeneration area in relation to the cooling area, it is possible to reduce the regeneration power duration or the heating power by 50%. The regeneration phase is put into operation only every second cooling phase. According to measurements in test mode, this economic process saves about 38% of the energy consumption of the system.

According to a further particular feature of the invention, the air flow for cooling after the drying or dehumidification phase is diverted from the exhaust air flow. By this measure, the cooling effect due to the dry air can be improved. Any re-humidification by outside air is avoided.

According to one embodiment of the invention, a central, hollow-wave-like trained area of the wheel dryer is used as a heat exchanger and a regeneration of the drying or adsorbent necessary, produced in a regeneration blower, Re 2/12 Austrian Patent Office AT509 475B1 2012-01 -15 generations air flow before it enters the wheel dryer through this hollow shaft. This sophisticated, innovative design results in a further energy consumption minimization of the system.

According to a further embodiment of the invention, the circular segments of the drum are divided with radial partitions into individual cells. As a result, smaller, spatial units are available in the process process, whereby a more optimal control or regulation of the overall process is achieved.

The invention is also based on the object to provide a device for carrying out the above-indicated method for drying bulk material, which on the one hand avoids the cited prior art disadvantages and on the other hand, increases the efficiency of the system.

This object is also achieved by the invention.

The device according to the invention for carrying out the method is characterized in that the drum of the wheel dryer has individual cells and the individual cells of the drum of the wheel dryer are formed from sheets, wherein at the radial outer and inner jacket of the drum fitting clamping plates of each cell U- have shaped cross-section and are arranged axially on the inner wall and the legs of the U-shaped clamping plates are inclined outwardly and provided as partitions of the individual cells dividers are positioned by the clamping action of adjacent legs of two adjacent U-shaped clamping plates and seal line by line. With the invention, it is now possible to combine a simple structural design with the simplest material components, namely sheets, to a very economical solution, whose functionality is also the robust operation. The inner construction of the drum, which is manufactured using simple metal sheets, is not only wear-resistant but of course also requires little maintenance. Due to the positioning of the separating plates via the clamping effect, a sealless axial sealing of the individual cells is achieved. It is also obvious that a rational, economical production is possible by the processing of simple sheets with simple sheet metal working machines. Another serious advantage of this sheet metal construction inside the drum is that all thermal expansions due to the temperature differences are absorbed by the elastic construction of the drum.

Another advantage of this sheet metal construction is the fact that in an operational exchange of the adsorbent only the adsorbent has to be disposed of in a landfill. The drum housing with its internal structure in which the adsorbent is contained in operation, of course, can be reused. This refilling gives a huge advantage in terms of environmental impact. Furthermore, of course, the cost of such renewal are drastically reduced.

With the invention impeccable quality with high reliability and consistent functionality with sophisticated construction is connected to optimum efficiency.

According to a particular embodiment of the invention, circumferentially at least three, preferably six, in particular 36, cells are provided. As a result, a continuous overall process is advantageously possible, wherein an optimal uniform dew point over the operating time is achieved by the small spatial units.

According to a further feature of the invention, the wheel dryer is divided into at least three circle segments, wherein the area of a circle segment for drying or dehumidifying the exhaust air flow, the area of the second circle segment for heating the adsorbent and the area of the third circle segment for cooling of the adsorbent serves. By this division into corresponding areas of the drum, a minimization of the space requirement is achieved because the process process interrupting intermediate steps, by lines to the individual process steps omitted. It also optimizes the energy budget of the overall process.

According to a further particular feature of the invention, the wheel dryer is provided at both axial ends of the drum with a lid, wherein each cover has the connections for the air ducts at both 3/12 Austrian Patent Office AT509 475 B1 2012-01-15. Such a construction of the wheel dryer brings a straight flow for all air currents with it, whereby the lowest pressure losses are given. Furthermore, the largest possible cross-section is used as an active zone. As is known per se, the residence time of the air should be longer and thus the flow velocity in the active zone should be low. These conditions can be fulfilled with this construction of the wheel dryer.

According to one embodiment of the invention, the two covers are stationary and between the covers and the rotating drum, a running disk is provided with a seal, in particular a sandwich seal.

According to another particular feature of the invention, the wheel dryer in its central region on a hollow shaft and this hollow shaft is as a heat exchanger, optionally filled with a wire mesh or stainless steel wool o. The like., Is provided. As already mentioned above, this intelligent construction can save energy and increase efficiency. In addition, the indicated filling materials have proven to be ideal for the heat exchanger function.

The invention will be explained in more detail with reference to an embodiment, which is illustrated in the drawing.

Figure 1 is a schematic of the air ducts, Figure 2 is a view of a wheel dryer, Figure 3 is a plan view of the wheel dryer with lid removed, and Figure 4 a Detail with cells of a drum of the wheel dryer.

1, the air ducts for the process for drying bulk material, in particular solids, such as granules, powders, grains, films, snippets, o. The like., Preferably, plastic granules are shown schematically. The plastic granules are dried in a drying silo 9 by means of a stream of air. For drying the outgoing from the drying silo 9 exhaust air stream 5 and the return air in the drying or dehumidifying 14, the exhaust air stream 5 via a filter 10 and a process fan 11 with the, a dry or adsorbent-containing, wheel dryer 1 connected. In the wheel dryer 1, the exhaust air flow 5 is dried. The exhaust air stream 5 is fed as dry air stream 12 to the drying silo 9 again.

The adsorbent is regenerated in the wheel dryer 1, in the regeneration phase 15 and then, in the cooling phase 16, cooled. For regeneration of the adsorbent, the regeneration air stream 6 is passed via a filter 17 and a regeneration blower 18 via the heat exchanger 13, heated via a heater 19 and then fed to the wheel dryer 1. For subsequent cooling of the adsorbent, a portion is diverted from the dry air stream 12 as air stream 7 for cooling and fed to the wheel dryer 1.

The drying or dehumidifying 14 for the exhaust air stream 5 is continuously performed in continuous operation. Preferably, the cooling phase 16 of the adsorbent in parallel in continuous operation for drying or dehumidification 14, performed. The regeneration phase 15 with the heating of the absorbent is carried out in the interval mode.

As already mentioned, zeolite requires for regeneration, ie for dehumidifying and drying a temperature above 200 ° C. For the regeneration of a certain amount of zeolite, therefore, a certain amount of energy, depending on temperature, time and air flow, necessary. Due to the degree of moisture of the zeolite, the optimum energy consumption can therefore be determined. An energy supply beyond the saturation range thus brings not much better efficiency and is a waste of energy. As is known per se, the energy consumption of the drying process in the drying or dehumidifying phase 14 is very much determined by the heat output in the regeneration phase 15.

According to the philosophy underlying the invention, namely to maintain the quality standard of the dry air to existing plants at least, however, to increase the efficiency, it is deliberately differentiated in the drying process between strong and less heavily loaded drying tasks. According to this conclusion, according to the present inventive method, the regeneration phase is run at less heavily loaded drying tasks in the interval mode. That is, the heater 19 for heating the absorbent and optionally the associated fan are deliberately switched off for a period of time. With such an interval operation, the curve for the dew point runs only insignificantly different from the ideal curve, but the deviation for the quality standard is not noticeable.

By a deliberate interpretation that the area for the regeneration phase 15 is at least equal, but preferably greater than the area for the cooling phase 16, the heater 19 and the regeneration blower 18, when operating the cooling phase 16 and the drying process phase of the absorbent to be switched off.

In a preferred embodiment, described later in more detail, in which the regeneration area is twice the size of the cooling area, the regeneration phase 15 can be shut down every second cooling period, thereby achieving a 50% energy saving.

The wheel dryer 1 is always stopped in the cooling-16 or regeneration phase 15. After completion of the cooling 16 or regeneration phase 15, the cooling area is further indexed. During the standstill of the wheel dryer 1, both the cooling 16 and the drying or dehumidifying 14 is in operation.

2, the wheel dryer 1 consists of a rotatable drum 2 which is provided at both axial ends, each with a lid 3, 4, wherein each cover 3, 4, the connections for the air ducts 5, 6, 7. The drum 2 is rotatable with a belt drive on a drive motor 8, wherein the two covers 3, 4 are stationary. The central region of the wheel dryer 1 is formed as a hollow shaft and has the function of a heat exchanger 13th

The wheel dryer 1 is part of a device for drying bulk material, in particular solids, such as granules, powders, grains, films, snippets, o. The like., Preferably plastic granules. The device furthermore comprises a drying silo 9 through which an air stream flows. The air guide is shown schematically in FIG. For drying, in the drying or dehumidifying phase 14, of the outgoing from the drying silo 9 exhaust air stream 5 and the return air of the exhaust air stream 5 via a filter 10 and a process fan 11 with, containing a dry or adsorbent , Wheel dryer 1 connected. In the wheel dryer 1, the exhaust air flow 5 is dried. The exhaust air stream 5 is fed as dry air stream 12 to the drying silo 9 again.

The adsorbent is regenerated in the wheel dryer 1, in the regeneration phase 15 and then, in the cooling phase 16, cooled. For regeneration of the adsorbent, the regeneration air stream 6 is passed via a filter 17 and a regeneration blower 18 via the heat exchanger 13, heated via a heater 19 and then fed to the wheel dryer 1. For subsequent cooling of the adsorbent, a portion is diverted from the dry air stream 12 as air stream 7 for cooling and fed to the wheel dryer 1.

According to FIG. 3, the wheel dryer 1, which is open at the top, that is without a cover 3, is shown. The drum 2 is rotated or clocked via the drive motor 8 and the belt drive. The wheel dryer 1 or the drum 2 is divided into at least three circular segments, the area of a circular segment for drying or dehumidifying, ie the drying or dehumidifying phase 14, for the exhaust air flow 5, the area of the second circular segment 5 / 12 Austrian Patent Office AT509 475 B1 2012-01-15 used for heating, the regeneration phase 15 of the adsorbent and the area of the third circle segment for cooling, the cooling phase 16, of the adsorbent. In the central region of the wheel dryer 1, the heat exchanger 13 in the form of a heat exchanger 13 hollow shaft, a wire mesh or stainless steel wool o. The like. Be provided. The range of drying or dehumidifying is about 240 arc degrees, the range for heating about 80 arc degrees and the range of cooling about 40 degrees arc.

Between the covers 3, 4 and the rotating drum 2 is a running disk with a seal 20, in particular a sandwich seal, which serves as an elastic compensation element, is provided.

4, the inner life of the drum 2 is shown in a detailed view. The drum 2 is divided into individual cells 21, wherein the individual cells 21 of the drum 2 of the wheel dryer 1 are formed from sheets. At the radial outer and inner shells 22, 23 of the drum 2 are clamping plates 24 which have a U-shaped cross-section. The clamping plates 24 are arranged axially on the inner wall of the drum 2, that is to say on the outer casing 22 and on the inner casing 23. The legs 25 of the U-shaped clamping plates 24 are inclined outwardly so that they press after their insertion into the drum 2 with tension on the adjacent leg 25 of the adjacent clamping plate 24. As partitions of the individual cells 21 separating plates 26 are provided. By the clamping action of adjacent legs 25 of two U-shaped clamping plates 24 lying against each other, the separating plates 26 are positioned and sealed line by line. In this embodiment shown, 36 cells are provided circumferentially. Of course, in the extreme case, three, for the three phases, or six cells 21 would be conceivable.

According to the following Table 1, this process is illustrated in a drum 2 with 36 cells 21.

Table 1:

Drum lingers drum lingers f \ E ® - £ o > z s P £ m ff * Έ -O £ ® ® E E a > ® E §, c ö »2 (o 2 ω

repeat cycle

Desired humidification and cooling fan ON ON I Regeneration fan ON OFF 1 Regeneration ON OFF 1 Heating T Regeneration of 3 cells I I Calibration Heating and cooling Blower from I • l Cool 4 of 8 denested cells last 4 of the 8 reg cells dehumidification phase

The timing of the drum 2 once by five and the next by four cells 21 results from the fact that the boundary cell between the individual phases in the drum 2 are not in the active zone (see FIG. 3). 6/12

Claims (11)

Austrian Patent Office AT509 475 B1 2012-01-15 Claims 1. A method for drying bulk material, in particular solids, such as granules, powders, grains, films, chips, o. The like., Preferably plastic granules, in a drying silo by means of an air flow, wherein the from the drying silo exiting exhaust air stream or the return air in a drying or adsorbent-containing drying cell, preferably a wheel dryer, dried and fed back to the bulk material as a dry air stream and in the wheel dryer further regenerates the adsorbent and is cooled, wherein a rotatable drum of the wheel dryer is divided into at least three circle segments, wherein the area of a circle segment for drying or dehumidifying the exhaust air flow, the area of the second circle segment for heating the adsorbent and the area of the third circle segment for cooling the adsorbent is used marked in characterized in that the drying or dehumidifying phase (14) for the exhaust air flow (5) and preferably the cooling of the adsorbent run in parallel, in particular continuously in continuous operation, and the regeneration phase (15) is carried out with the heating of the absorbent in the interval operation, wherein the drum (2) of the wheel dryer in the cooling (16) and regeneration phase (15) is stopped and after completion of the cooling (16) or regeneration phase (15) is further clocked by a selectable range, preferably the cooling area, and in that the area for heating is set at least equal to or greater, preferably twice, than the area of cooling. 2. The method according to claim 1, characterized in that the range of drying or dehumidifying about 240 degrees, the range for heating about 80 degrees and the range of cooling is about 40 degrees arc. 3. The method according to claim 1 or 2, characterized in that the air flow (7) for the cooling after the drying or dehumidifying phase (14) is diverted from the exhaust air flow (12). 4. The method according to any one of claims 1 to 3, characterized in that a central, hollow-wave-shaped region of the wheel dryer (1) is used as a heat exchanger (13) and a necessary for the regeneration of the dry or adsorbent, in a regeneration blower ( 18) generated, regeneration air flow (6) before it enters the wheel dryer (1) is guided through this hollow shaft. 5. The method according to any one of claims 1 to 4, characterized in that the circular segments of the drum (2) are divided with radial partitions into individual cells (21). 6. Device for carrying out the method according to one of claims 1 to 5, characterized in that the drum (2) of the wheel dryer (1) individual cells (21) and the individual cells (21) of the drum (2) of the wheel dryer ( 1) are formed from sheets, wherein at the radial outer (22) and inner sheath (23) of the drum (2) adjacent clamping plates (24) of each cell (21) have U-shaped cross-section and are axially disposed on the inner wall and the legs (25) of the U-shaped clamping plates (24) are inclined outwards and provided as partitions of the individual cells (21) separating plates (26) by the clamping action of adjacent legs (25) of two adjacent U-shaped clamping plates (24) are positioned and line by line. 7. Device according to claim 6, characterized in that circumferentially at least three, preferably six, in particular 36, cells (21) are provided. 8. Device according to claim 6 or 7, characterized in that the wheel dryer (1) is divided into at least three circle segments, wherein the area of a circle segment for drying or dehumidifying the exhaust air stream (5), the area of the second circle segment for heating of the adsorbent and the area of the third circle segment serves to cool the adsorbent. 7/12 Austrian Patent Office AT509 475 B1 2012-01-15 9. Device according to one of claims 6 to 8, characterized in that the wheel dryer (1) is provided at both axial ends of the drum (2) each with a lid (3, 4), wherein each cover (3, 4) the Having connections for the air ducts (5, 6, 7). 10. Device according to one of claims 6 to 9, characterized in that the two covers (3, 4) are stationary and between the covers (3, 4) and the rotating drum (2) has a running disk with a seal (20), in particular, a sandwich seal is provided. 11. Device according to one of claims 6 to 10, characterized in that the wheel dryer (1) in its central region has a hollow shaft and this hollow shaft as a heat exchanger (13), optionally filled with a wire mesh or stainless steel wool o. The like., Is provided , 4 sheets of drawings 8/12